Biodegradable synthetic turf yarn

ABSTRACT

The invention is directed to a synthetic turf yarn, to a method of preparing said synthetic turf yarn, to artificial turf comprising said synthetic turf yarn, and to a method of preparing artificial turf. 
     The synthetic turf yarn of the invention comprises an aliphatic polyester and a copolyester of butanediol, terephthalic acid and a linear aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, and sebacic acid.

The invention is directed to a biodegradable synthetic turf yarn, to a method of preparing said biodegradable synthetic turf yarn, to artificial turf comprising said biodegradable synthetic turf yarn, and to a method of preparing artificial turf.

Artificial turf (also known as synthetic turf or artificial grass) is widely used in many applications including sports fields and landscaping as an alternative to (natural) grass. However, artificial turf is also used, e.g., on balconies, patios, pathways, playgrounds, etc. In particular on sports fields, artificial turf combines playing characteristics, look and feel of natural grass, with the advantages of increased frequency of usage, extra revenue generation, safety, longer playing sessions, fewer cancelled games, and lowest cost per playing day.

Artificial turf also offers some benefits for the environment. For example, real grass requires a lot of water whereas artificial turf does not. Additionally, real grass requires regular maintenance to keep it healthy and beautiful. Such maintenance typically involves fuel operated lawn mowers, trimmers, scarifiers, etc., that emit greenhouse gases. Further, artificial turf does not require weed killers, pesticides, fertilisers and herbicides, which may be harmful to the environment. Nonetheless, improvements can be made in order to make artificial turf more environmentally friendly.

In particular, the materials used to prepare artificial turf can be improved. At present, most of the artificial turf is still prepared from polyolefins, and more in particular polyethylene and polypropylene. There have been research efforts to make artificial turf more sustainable, for example, by developing recyclable artificial turf.

There also have been some attempts to replace rubber infill that is typically used in artificial turf for sports fields in order to support the grass fibres, and add dimensional stability. Typically, such infill material is made from styrene-butadiene rubber (SBR), which has excellent elasticity properties and very good resistance to atmospheric and chemical agents. One of such attempts to replace the rubber infill with other material is, for example, WO-A-2018/016956, which discloses an artificial turf with granular infill that is made of a foam material comprising polylactic acid or a derivative thereof. Polylactic acid is a bio-based and biodegradable material.

Over the years, plastics have brought economic, environmental and social advantages. However, their popularity has also meant a rise in plastic waste, which brings its own economic, environmental and social issues. Plastic waste has serious ecological impact. Plastic waste may be send to landfill (i.e. a disposal site for materials through burial) or may be incinerated, but both of these options still have serious implications for the environment. Another option is recycling, but recycling processes often lead to products of lower quality and economic value. Recycling of plastic products is therefore often termed ‘downcycling’. Additionally, much plastic waste is only recycled once or twice before ending up in landfill or being incinerated.

Redesigning plastic products could help alleviate some of the problems associated with plastic waste. One of the current developments is to seek biodegradable alternatives for plastic materials, while maintaining (or even improving) the materials properties.

It would be desirable to provide a synthetic turf yarn that is biodegradable, such that when pieces of the yarn end up in the environment these pieces fully degrade under the influence of bacteria and fungi.

In the art, there have been some attempts to provide biodegradable artificial turf.

For example, WO-A-2007/114686 discloses a synthetic fibre for use in an artificial grass lawn that is at least partially made of a biodegradable material. The biodegradable material can be a starch component, optionally combined with an aliphatic polyester such as polylactic acid to influence the biodegradability over time. Polylactic acid, however, is known for its relatively low flexibility and impact strength.

KR-B-101 855 284 discloses an artificial turf structure that is prepared using polybutylene succinate-co-adipate (PBSA) and polybutylene succinate (PBS) as biodegradable material.

Despite these efforts there remains a need for further biodegradable synthetic turf yarns, in particular having good processability. Further, there is a need for biodegradable synthetic turf yarns that excel in mechanical properties, such as modulus of elasticity and/or resilience.

Objective of the invention is to address one or more of these needs in the art.

The inventors found that this objective can, at least in part, be met by synthetic turf yarn that comprises an aliphatic polyester and combined with a specific biodegradable polyester.

Accordingly, in a first aspect the invention is directed to a synthetic turf yarn, comprising an aliphatic polyester and a copolyester of butanediol, terephthalic acid, and a linear aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, and sebacic acid.

The inventors surprisingly found that the defined polyesters allow to prepare synthetic turf yarn that has excellent properties. In particular, the material used by the inventors allows approach the properties of conventional synthetic turf yarn that is prepared from linear low density polyethylene, in particular with respect to modulus of elasticity. At the same time, the polyester materials used in synthetic turf yarn are biodegradable. If small pieces of the material would end up in the environment, then these bacteria and fungi will consume the material leaving no (or hardly any) detrimental remnants. The inventors further found that the combination of an aliphatic polyester and the defined polyesters provide superior processability.

The synthetic turf yarn of the invention comprises a copolyester of butanediol, terephthalic acid, and a linear dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, and sebacic acid. Each of these copolyesters have high flexibility, excellent impact strength, and good melt processability. Advantageously, these copolyesters exhibit good biodegradability of about one year in soil, sea water and water with activated sludge.

Examples of suitable copolyester that can be used in accordance with the invention include copoly(butylene succinate-co-terephthalate), copoly(butylene adipate-co-terephthalate), and copoly(butylene sebacate-co-terephthalate). Copoly(butylene succinate-co-terephthalate) is also referred to as polybutylene succinate terephthalate (or PBST). Copoly(butylene adipate-co-terephthalate) is also referred to as polybutylene adipate terephthalate (or PBAT). Copoly(butylene sebacate-co-terephthalate) is also referred to as polybutylene sebacate terephthalate (or PBSeT).

Preferably, the copolyester is selected from copoly(butylene adipate-co-terephthalate) and copoly(butylene sebacate-co-terephthalate). More preferably, the copolyester is copoly(butylene adipate-co-terephthalate). PBAT is commercially available as Ecoflex™ from BASF, as Eastar Bio® from Eastman Chemical, as Origo-Bi® from Novamont, as EcoPond® from Kingfa, and as Ecoword® from Jinhui.

The content of the copolyester in the synthetic turf yarn can be in the range of 30-100% by total weight of the yarn, preferably 40-98%, such as 50-95%, or 60-90%. The amount of copolyester also depends on the intended application of the artificial turf in which the synthetic turf yarn is to be used. In particular, the copolyester provides the synthetic turf yarn with softness and elasticity.

As additional polymer the synthetic turf yarn comprises an aliphatic polyester, preferably a biodegradable aliphatic polyester, such as one or more selected from the group consisting of polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene sebacate (PBSe), and polybutylene succinate sebacate (PBSSe). Especially good results have been obtained with polybutylene succinate. It was found that such aliphatic polyesters blend surprisingly well with the copolyesters as defined herein. PBS is commercially available as BioPBS™ from Mitsubishi Chemical. PBA is commercially available from Sigma-Aldrich.

The content of the additional aliphatic polyester in the synthetic turf yarn can be in the range of 1-70% by total weight of the synthetic turf yarn, preferably 2-60%, such as 5-50%, or 10-40%. Also the amount of the aliphatic polyester depends on the intended application of the artificial turf in which the synthetic turf yarn is to be used. In particular, the aliphatic polyester provides the synthetic turf yarn with stiffness.

The weight ratio between the copolyester and the aliphatic polyester in the synthetic turf yarn can suitably be 40:60 to 90:10, preferably 45:55 to 80:20, such as 50:50 to 70:30.

Preferably, the synthetic turf yarn of the invention comprises a combination of polybutylene adipate terephthalate (or copoly(butylene adipate-co-terephthalate)) and polybutylene succinate. Such a combination was found to exhibit particularly good processability. The amounts and weight ratios of this specific copolyester and aliphatic polyester can then be as described above. In terms of achieving an optimum balance of both mechanical properties and processability it is preferred that the synthetic turf yarn of the invention comprises a combination of copoly(butylene adipate-co-terephthalate) and polybutylene succinate in a weight ratio of copoly(butylene adipate-co-terephthalate) to polybutylene succinate of 1.0 or lower, such as 0.8 or lower, 0.6 or lower, 0.5 or lower, 0.4 or lower, such as in the range of 0.1-0.8, in the range of 0.1-0.6, in the range of 0.1-0.5, or in the range of 0.1-0.4.

Optionally, it is possible to include one or more further biodegradable polymers in the synthetic turf yarn of the invention, for example, in order to finetune the degradation rate of the material in soil. Suitable examples of such further biodegradable polymers include polylactic acid) (PLA), polyhydroxyalkanoates (PHA), and starch polymers.

A means of increasing the degradation rate of the material is further to include natural fibre in the synthetic turf yarn of the invention. Examples of suitable natural fibres that may be employed include bast fibres, leaf fibres, grass fibres, straw fibres and seed fibres. Depending on the intended degradation rate, such natural fibres may be used in amounts of up to 20% by total weight of the yarn, preferably 0.5-15, such as 1-10%, or 2-8%.

Further additives may be included in the synthetic turf yarn of the invention as desired. Examples of suitable additives include fillers, antioxidants, compatibilisers, flame retardants, colouring agents, heat stabilisers, processing aids, antioxidants, UV stabilisers, UV absorbers, and pigments. Such additives may be present in amounts up to 10% by total weight of the yarn, such as 0.01-10%, 0.05-8%, or 0.1-5%. If additives are used, it is preferred to use additives that are environmentally friendly, and more preferably biodegradable.

Suitable fillers (in particular inorganic fillers), for instance, include talc, mica, wollastonite, calcium carbonate, barium sulphate, magnesium carbonate, clay, alumina, silica, calcium sulphate, carbon fibres, glass fibres, metal fibres, silica sand, carbon black, titanium oxide, magnesium hydroxide, zeolite, molybdenum, diatomaceous earth, sericite, calcium hydroxide, calcium sulphite, sodium sulphate, bentonite and graphite. Such fillers may be used in combination with the copolyester to increase hardness of the resulting synthetic turf yarn. Fillers may be present in an amount of % or less by total weight of the yarn, preferably 3% or less, such as 2% or less, or 1% or less. High amounts of filler can negatively affect properties such as wear resistance, roughness, resilience and/or stiffness.

Examples of pigments include inorganic pigments that are suitably coloured to provide an aesthetic appeal including various shades of green, white (TiO₂, rutile), iron oxide pigments, and any other colour.

Examples of antioxidants include: hindered phenols, phosphites and phosphonites, thio compounds, various siloxanes, alkylated cliphenylamines, and other hindered amine antidegradants or stabilisers. Antioxidants can be used in amounts of 0.1 to 5% by total weight of the yarn.

Examples of processing aids include metal salts of carboxylic acids, fatty acids, fatty amides, polyethylene wax, oxidized polyethylene wax, polymers of ethylene oxide, copolymers of ethylene oxide and propylene oxide, vegetable waxes, petroleum waxes, non-ionic surfactants, and polysiloxanes. Processing aids can suitably be used in amounts of 0.05-5% by total weight of the yarn.

Examples of UV stabilisers and UV absorbers include hindered amine light stabilisers, benzophenone, benzotriazole, hydroxyphenyl triazine, 2-(2′-hydroxyphenyl)benzotriazoles, Uvinol 3000, Tinuvin P, Irganox 1098, Uvinol 3008, Lavinix, BHT, Tinuvin 320, Irganox 1010, Irganox 1076, and Irgafos 168.

The thickness of the synthetic turf yarn can be 0.05 to 0.80 mm, such as 0.06-0.70, preferably 0.08 to 0.60 mm, or 0.10 to 0.50 mm. The width of the synthetic turf yarn can be 0.5-15 mm, such as 0.7-12 mm, preferably to 10 mm, 1.0 to 8.0 mm, 1.2 to 5.0 mm, or 1.5 to 3 mm.

The synthetic turf yarn of the invention suitably has good flexibility and/or resilience. In particular, the tenacity (i.e. ratio of the breaking strength to the linear density of the unstrained specimen, expressed in centinewtons per tex) of the synthetic turf yarn, as measured at break according to BS EN 13864:2004, is preferably in the range of 1-50 cN/tex, preferably 3-30 cN/tex, more preferably 5-20 cN/tex.

The tenacity can be finetuned by inclusion of the aliphatic polyester. Higher content of aliphatic polyester will lead to higher tenacity values.

A further parameter that can be used to adapt the properties of the material is the amount of applied stretching. This can range, for instance, from 2-9%, preferably 3-8%, such as 4-7%.

In a further aspect, the invention is directed to a method of preparing a synthetic turf yarn according to the invention, comprising extruding a composition comprising an aliphatic polyester and a copolyester of butanediol, terephthalic acid and a linear aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, and sebacic acid. The composition may comprise or may consist of the combination of aliphatic polyester and copolyester.

Synthetic turf yarn of the invention can be prepared from tapes or from filaments. Both preparation processes involve extrusion.

In tape preparation, the polymer composition is extruded into a film which is subsequently cut into fibres or tapes. The film may be prepared by any conventional film formation process including extrusion procedures, such as cast film or blown film extrusion, lamination processes or any combination thereof. The film may be a monolayer or multilayer film, e.g. a coextruded multilayer film. In the case of a multilayer film, preferably, the film layers may comprise the same or different polymer composition. The tapes into which the films are cut can have a thickness of up to 200 μm, such as 10-150 μm, 25-125 μm, or 50-100 μm. The tapes can have a width of up to 2.0 cm, such as 0.1-1.8 cm, 0.2-1.5 cm, 0.4-1.2 cm, or 0.5-1.0 cm.

In filament preparation, the polymer composition is extruded in an extruder that is equipped with a specific turf yarn die that typically has multiple single holes for individual filaments distributed over a circular or rectangular spin plate. The shape of the holes corresponds to the desired yarn cross-section profile, including for example, rectangular, dog-bone, and V-shaped. Multiple individual filaments may be wrapped or twisted together into a synthetic turf yarn. Alternatively, the yarn may consist of a single filament. The filaments can have a thickness of 10-1000 μm, such as 50-800 μm, 100-700 μm, or 200-500 μm. The filaments can have a width of up to 3 mm, such as 0.1-2.5 mm, 0.2-2 mm, or 0.5-1.5 mm.

Accordingly, the composition can be extruded into a film which is subsequently cut into fibres or tapes, or composition can be extruded into filaments (and optionally multiple filaments may be weaved), to produce a synthetic turf yarn.

If the composition to be extruded has multiple components, then the method suitably comprises a step of blending the different components into a composition prior to the extrusion step. If necessary, blending may be accompanied by exposure to ultrasound in order to increase the homogeneity of the blend.

In yet a further aspect, the invention is directed to artificial turf comprising the synthetic turf yarn according to the invention.

The artificial turf can optionally comprise infill material. It is preferred that such infill material comprises or is a natural material, a biodegradable material, or any combination thereof. Natural infill material includes, e.g., silica (sand), cork, coconut fibre, rice husks, walnut shells, olive stones, and combinations thereof. Biodegradable infill material is, for example, commercially available as GreenFill from EdelGrass.

The artificial turf of the invention can be prepared by inserting tufts of synthetic turf yarn according to the invention in an artificial turf backing. Accordingly, tufts are formed by clusters of yarn or fibre drawn through a fabric of the backing and projecting from the surface in the form of loops or cut yarn. The tufts of yarn are typically held in place in the backing by an adhesive, commonly referred to as a back coat, that is normally applied to the backside of the backing to enhance locking or anchoring of tufts to the backing. Suitable material for the back coat includes, for instance, carboxylated styrene-butadiene rubber (SBR) latex.

The artificial turf as described herein is particularly suitable for landscapes, such as commercial, recreational, and residential landscapes, parks, sports fields, such as sports fields for contact sports, ball sports, and athletics, playgrounds, and gardens.

All references cited herein are hereby completely incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. For the purpose of the description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include any combination of the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

When referring to a noun in the singular, the plural is meant to be included, or it follows from the context that it should refer to the singular only.

Preferred embodiments of this invention are described herein. Variation of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject-matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.

For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

The invention will now be illustrated by means of the following examples.

EXAMPLES

Two different biodegradable polymers PBAT and PBS with varying mechanical properties, from rubbery to rigid were compounded in different concentrations. The compositions are shown in Table 1 below.

TABLE 1 Example PBAT PBS No. (parts by weight) (parts by weight) 1 11 100 2 25 100 3 50 100 4 100 100 5 100 75 6 100 50 7 100 25 8 100 11 9 100 0

The goal of these experiments was to obtain biodegradable artificial grass with properties comparable with the currently used linear low density polyethylene (LLDPE) types of grass or at least suitable enough for making artificial grass.

The two polymers were melt blended in different ratios on a twin screw extruder (24 mm Collin Laboratory extruder) and directly small tapes were produced.

Dimensions of the unstretched tapes were around 10-13 mm width and a thickness of 400-500 μm. The unstretched tapes were then (in-line) heated in an oven and stretched 3-6 times to obtain increased mechanical properties.

Depending on the stretch ratio the end tapes were between 2-4 mm width and a thickness of 150-200 μm.

From these different polymer tapes with different polymer ratios, mechanical properties were measured, and the tapes were evaluated on miscibility by DSC and optical inspection.

Analysis of these examples showed that the tenacity of the samples increased with increasing content of the aliphatic polyester, PBS. The examples having a mix of the copolyester PBAT and the aliphatic polyester PBS were found to have particularly good processability. Particularly good results in terms of a good combination of mechanical properties and processability were achieved with examples comprising both PBAT and PBS, in particular wherein the weight ratio of PBAT to PBS was 1.0 or lower (i.e. Examples 1-4). 

1. Synthetic turf yarn, comprising an aliphatic polyester and a copolyester of butanediol, terephthalic acid and a linear aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, and sebacic acid, said synthetic turf yarn further comprising.
 2. Synthetic turf yarn according to claim 1, wherein said linear dicarboxylic acid is sebacic acid and said copolyester is copoly(butylene sebacate-co-terephthalate).
 3. Synthetic turf yarn according to claim 1, wherein said linear dicarboxylic acid is adipic acid and said copolyester is copoly(butylene adipate-co-terephthalate).
 4. Synthetic turf yarn according to claim 1, wherein the content of said copolyester in said yarn is 30-100% by total weight of the yarn, preferably 40-98%, such as %, or 60-90%.
 5. Synthetic turf yarn according to claim 1, wherein said aliphatic polyester comprises or is one or more selected from the group consisting of polybutylene succinate, polybutylene adipate, or polybutylene sebacate.
 6. Synthetic turf yarn according to claim 1, wherein said aliphatic polyester is polybutylene succinate.
 7. Synthetic turf yarn according to claim 1, wherein the content of said aliphatic polyester in said yarn is 1-70% by total weight of the yarn, preferably 2-60%, such as 5-50%, or 10-40%.
 8. Synthetic turf yarn according to claim 1, wherein the weight ratio between the copolyester and the aliphatic polyester is 40:60 to 90:10, preferably 45:55 to 80:20, such as 50:50 to 70:30.
 9. Synthetic turf yarn according to claim 1, wherein said copolyester is copoly(butylene adipate-co-terephthalate) and wherein said aliphatic polyester is polybutylene succinate.
 10. Synthetic turf yarn according to claim 9, wherein the weight ratio of said copoly(butylene adipate-co-terephthalate) to said polybutylene succinate in the synthetic turf yarn is 1.0 or lower, such as 0.8 or lower, 0.6 or lower, in the range of 0.1-0.5, or in the range of 0.1-0.4.
 11. Synthetic turf yarn according to claim 1, further comprising natural fibre.
 12. Synthetic turf yarn according to claim 11, wherein said natural fibre is one or more selected from the group consisting of bast fibres, leaf fibres, grass fibres, straw fibres and seed fibres.
 13. Synthetic turf yarn according to claim 11, wherein said natural fibre is present in an amount of up to 20% by total weight of the yarn, preferably 0.5-10, such as 1-5%.
 14. Synthetic turf yarn according to claim 1, further comprising one or more additives selected from the group consisting of fillers, compatibilisers, flame retardants, colouring agents, heat stabilisers, processing aids, antioxidants, UV-stabilisers, and pigments.
 15. Synthetic turf yarn according to claim 1, wherein the yarn has a tenacity of the synthetic turf yarn, as measured at break according to BS EN 13864:2004, in the range of 1-50 cN/tex, preferably 3-30 cN/tex, more preferably 5-20 cN/tex.
 16. Method of preparing a synthetic turf yarn according to claim 1, comprising extruding a composition comprising an aliphatic polyester and a copolyester of butanediol, terephthalic acid and a linear aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, and sebacic acid, wherein said extruding preferably comprises extruding the composition into a film which is subsequently cut into fibres or tapes, or extruding the composition into filaments, and optionally weaving multiple individual filaments, to produce a synthetic turf yarn.
 17. Artificial turf, comprising synthetic turf yarn according to claim
 1. 18. Artificial turf according to claim 17, further comprising a biodegradable infill material.
 19. Method of preparing an artificial turf, comprising inserting tufts of synthetic turf yarn according to claim 1 in an artificial turf backing, and applying an adhesive to the back side of the backing. 